function* oneDigitPrimes() {
  yield 2;
  yield 3;
  yield 5;
  yield 7;
}

function* sequence(...iterables) {
  for (const iterable of iterables) {
    for (const v of iterable) {
      yield v;
    }
  }
}
console.log(`${[...sequence("abc", oneDigitPrimes())]}`); // a,b,c,2,3,5,7

function* sequence2(...iterables) {
  for (const iterable of iterables) {
    yield* iterable;
  }
}

console.log(`${[...sequence2("abc", oneDigitPrimes())]}`); // a,b,c,2,3,5,7
